NO155569B - 0 BUILDING KIT FOR AA EQUIPMENT VEHICLES WITH A SYSTEM FOR AUTOMATIC MONITORING AND CONTROL OF WHEEL TIRE PRESSURE. - Google Patents

Description

The present invention generally relates to systems for inflating wheel tires and more specifically to a device for automatically regulating the pressure in vehicle wheels.

It is well known that traction for vehicles on soft ground can be greatly enhanced by reducing the pressure in the wheel tyres. By reducing the pressure, the bearing surface of the tires will increase and thereby increase the contact area between the tires and the terrain. It is also often desirable to reduce the pressure in the tires to increase comfort when driving on bad roads. On the other hand, higher pressure in the tires will reduce the rolling resistance and the temperatures in the tire layer .. on smooth roads and thus increase economy and safety.

It would be desirable to be able to adjust the pressure in the tires without having to stop the vehicle and manually pump up or let air out of the wheels. This is particularly the case for military vehicles which usually move in columns, many times under conditions where stopping the vehicle would delay the entire column. In addition, if the military vehicle is under enemy attack, it is of the utmost importance that the vehicle maintains its ability to maneuver

as long as possible. If a wheel is punctured by shooting or the like, it is necessary to be able to at least partially inflate the wheels very quickly, so that the vehicle remains usable.

Various automatic systems for pumping up

wheels have been used in the past to remedy one or more of these problems. Such a system was common equipment on

U.S. Army vehicles known as "Duk" which were used in the Second World War. This technique used a so-called Schrader valve system, where air pressure was delivered through long rod-like wires that protruded from the vehicle's wheel arches in the frame and fed air into rotating couplings connected to the outside of the hubs. Another wire from the inside edge of the rotary couplings was connected to valve stems in the inner hoses of the wheels.

One of the problems with this solution was its extreme vulnerability to damage because the wires carrying the air were exposed to the uneven terrain over which the vehicle traveled. The cables were exposed to breakage or damage by

come into contact with bushes, rocks or other vehicles.

In an attempt to improve this system, several attempts have been made to improve a delivery technique for the internal air pressure that would not be subject to such abuse. It is believed that some of the vehicles used in the U.S.S.R. and the associated countries have used systems for automatic inflation of wheels, where air from a compressed air source was passed through the wheel equipment and into the tyre. In addition, the following U.S. patents provide a representative but non-exhaustive list of various other solutions for automatic tire inflation systems: U.S. Pat. patent no. 2 693 841, 2 944 579,

2,976,906, 2,634,783, 2,634,782, 2,577,458, 2,849,047, 3,362,452, 1,800,780, 3,705,614, 2,715,430, 4,019,552 and 4,154,279.

One of the significant disadvantages of these different solutions is that they generally require considerable operator attention to achieve the desired air pressure. For the most part, these systems require an operator to operate a switch for inflation or deflation and then continuously check an air pressure gauge until the desired pressure is reached, at which point the operator must disengage the switch. Furthermore, nothing was arranged to accurately and automatically maintain the air pressure in the wheel when this was initially set in this operation. These problems are particularly acute when the vehicle is under enemy attack, where the soldier's time could be much better spent defending himself than monitoring instruments.

Equally unsatisfactory is the state of the art when it comes to solving the control of the inflation-discharge valve. Previously, only a control valve was usually used, which gradually opened or closed depending on the pressure differential between the desired and actual pressure inside the wheels. When e.g. the pressure differential decreased gradually closing the valve until equilibrium was reached. Unfortunately, this technique unduly increased the inflation or deflation cycle time, which is extremely important under combat conditions.

A simple and yet reliable seal for the air channels between the rotating and non-rotating parts of the wheel equipment has been difficult to produce in the past. Many of the previously known solutions have been relatively complex and difficult to put together. Commonly used air seals with one or more generally vertically running sealing tabs can tend to lift from their surfaces under high pressure and thereby destroy the entirety of the seal. Still other sealing structures were located outside the bearings and were exposed to harmful environmental conditions that reduced their useful life.

Many of the wheel fittings for internal air supply were connected to load-bearing parts (eg axles, stems) to form air ducts. This unfortunately reduces the strength of these parts. Some of the previously known solutions also required a new placement of the bearings in relation to their originally constructed placement and thereby often made it necessary to re-construct various parts at additional costs.

Many of the military vehicles that are still in use still have many years of service life left or they are still being manufactured. In some cases, it will be desirable to modify these vehicles at low cost to include a system for automatic inflation of the wheels. However, many of the previously known solutions are specifically designed for a specific application and cannot be easily incorporated into a conventionally used military vehicle such as the M809, M44A2 and M939 military vehicles.

The present invention is aimed at solving one or more of the problems described above, by means of a conversion kit that equips vehicles with a system for automatic monitoring and control of the wheel's tire pressure. In connection with the use of this conversion kit, a wheel assembly and means in the wheel assembly are described for placing a pair of sealing rings completely inside the hub bearings. The sealing rings include a flexible, mainly horizontally extending edge part which rests against non-rotating parts of the wheel equipment. An air duct from the non-rotating part to the rotating part of the wheel equipment is designed exclusively in non-load-bearing parts. This serves to provide a simple yet reliable rotating air seal construction in the transition area of the air passage where the non-rotating and rotating parts meet. In one embodiment, a sleeve is attached to a conventional hub and is used to attach the sealing rings so that standard vehicles can be converted to include such a system for automatic wheel inflation.

In another embodiment, which is also relevant in connection with the conversion kit, a hub is constructed from a single part of cast metal with an annular inner surface that delimits a central passage, through which a non-load-bearing spindle is guided. The hub is mounted for rotary movement about the spindle on a pair of mutually separated bearings. A shaft extends through the spindle and is connected to the hub to give it a turning motion. The hub includes a centrally located enlarged internal cavity. Means are arranged on the annular surface of the hub on both sides of the cavity for receiving a pair of annular sealing rings. A generally horizontally extending flexible lip seal extends from the inner circumference of each seal ring. The rings are held in place at least in part by receiving means in the annular inner surface of the hub. Preferably, the receiving means includes a shoulder and a separate groove, in which a snap ring is located. The sealing rings are held laterally in place between the projections and the snap rings. When held in this position, the horizontally extending flexible lip portion of the sealing rings rests against the outer surface of the spindle.

Part of the air channel is provided by means of a bore in the spindle. Compressed air is driven through the air channel into the enlarged central cavity in the hub and from there to the wheels. The relatively high air pressure within the central cavity serves to provide a large portion of the downward force on the lip portions of the seals to block air from passing between the rotating and non-rotating portions of the wheel gear.

In one embodiment, the outer surfaces of the sealing rings are coated with a rubber-like material. This rubber coating serves to provide an improved seal between the outer circumference of the sealing rings and the hub. The horizontally extending lip of the sealing ring may include a portion of "Teflon" on its contact surface to increase the life of the seals under lubrication-free conditions.

In accordance with the invention, there is thus provided a conversion kit which equips vehicles with a system for automatic monitoring and control of the tire pressure of the wheels, comprising an operating box mounted in the cabin of a vehicle and which includes manually operable selector means for selecting one of several preset pressure values for the wheels' tires and valve devices that provide inflation/discharge of air under pressure and are mounted on the vehicle, and the conversion kit is characterized by the features that appear in the subsequent claim 1. If the vehicle is not already equipped with wheel equipment designed for such an automatic pressure system, the conversion kit also include replacement and/or adaptation parts for the wheel equipment. The use of the kit according to the present invention allows an owner to improve his vehicle so that it includes such an automatic pressure system, and with minimal cost and labor effort.

These and further advantages of the present invention will be apparent to a person skilled in the art after reading the following description with reference to the drawings, where fig. 1 is a perspective view of a wheel equipment produced in accordance with use in connection with the invention, fig. 2 is a section of the wheel equipment shown in fig. 1, fig. 3 is a separated perspective view of parts of the wheel equipment, fig. 4 is a drawing which schematically shows the control system for regulating the air pressure in the wheels according to the pressure system, fig. 5 is a view similar to fig. 4, which schematically shows the pneumatic components in the control system, fig. 6 is an end view of a hub according to an alternative embodiment, fig. 7 is a section along the line 7-7 in fig. 6, fig. 8 is a section of a wheel equipment in accordance with an alternative embodiment and fig. 9 is a partial view on a larger scale of the rotary seal construction that can be used in both versions of the wheel equipment.

The set according to the present invention finds particular application in connection with military vehicles of the type shown in fig. 1. The vehicle 10 may be a five-ton M813 truck built for the U.S. Army by the applicants' company. On

fig. 1 shows a part of the vehicle 10 which comprises a front axle 12 which drives the wheel equipment 14, on which the wheel 16 is mounted. In fig. 1 also shows an air line 18 with a conventional air intake valve stem 20 and a manual shut-off valve 22.

It should be understood from the introduction that while this invention will be described in connection with a special type of vehicle, the invention can be used in a wider sense in other types of vehicles, such as buses, heavy-duty trucks, vans and the like. Therefore, the special designs described in the present text should not be taken as limiting examples.

In fig. 2 and 3, a wheel assembly 14 includes a tubular spindle 24, the inner part of which is slightly expanded to form a rear flange 26. The spindle 24 is stationary, i.e. it does not rotate, because the rear flange 26 is bolted to the vehicle undercarriage 28. The hub 30 is attached for rotational movement about the spindle 24 by means of conventional bearings 32, 33. The left bearing 32 is held in place by means of parts 35, 37 and 39. The hub 30 includes a centrally arranged cavity 34 therein. The wheel 16 is mounted around the outer circumference of the hub 30 using known techniques which include a bead lock 36. The shaft 12 passes through the hollow spindle 24. The inner part of the shaft 12, for a driven wheel, is connected to a suitable source of motive power , such as a differential. The outer end of the shaft 12 includes splines (not shown) which engage corresponding grooves in the drive flange 40. The drive flange 40 is in turn bolted to the hub 30 to impart rotary motion to the wheel 16 in accordance with the rotation of the shaft 12.

The wheel equipment thus described is conventional. In accordance with the present invention, the wheel assembly 14 can be easily adapted to provide a sealed rotating air coupling with a minimal amount of adaptation. An annular cuff 42 has its outer edges connected, for example by welding, to the hub 30, so that the cuff 42 generally bridges the central cavity 34 in the hub 30. The inner parts of the cuff 42 include two separate grooves for receiving locking rings 44, 46. The cuff 42 also forms projections 48 and 50 which respectively counteract the locking rings 44 and 46.

The combination locking ring and shoulder in the cuff 42 defines a seat for receiving the outer peripheral surfaces of sealing rings 52, 54. The sealing rings 52, 54 are in the form of annular channels with open ends having a rigidly constructed outer main part and a flexible inner lip seal preferably made of synthetic rubber. Garter springs 56, 58 provide radially inwardly directed pressure forces on the flexible lip seals which abut against the outer surface of the spindle 24. This device defines an inner chamber 60 which surrounds the spindle 24. The sealing rings 52, 54 will be discussed in more detail later.

Provision is now made to produce a sealed air channel between an intake 62 in the non-rotating part of the wheel equipment 14 and an outlet 6 4 in the rotating hub 30. A first bore 66 is drilled in the spindle 24, through substantially its entire length, preferably at using a rifle drill technique. The left part of the bore 66 is sealed with a plug 68. Another downwardly directed bore 70 in the flange 26 is drilled until it abuts the right part of the bore 66. A substantially L-shaped connection 72 is welded to the spindle to extend the bore 70, as that it can be easily connected to an air source provided by a hose 74. A substantially right-angled directed opening 76 extends between the chamber 60 and the first bore 66 in the spindle 24. The sleeve 42 similarly includes an opening 78, so that the air can stand in connection between the chamber 60 and the cavity 34. A third bore 80 is then drilled in the hub 30 which extends into the cavity 34 to form a passage between the threaded outlet 64 and the cavity 34.

Air supplied to the intake 62 passes through the bores 70 and 66 and then out through the opening 76 in the stationary part of the wheel equipment 14. The air then exits through the opening 15569 8

gene 76 and into the chamber 60. Air is prevented from escaping to the external environment by means of the cuff 42 and the air seals 52, 54 which rotate with the hub 30. When there is compressed air in the chamber 60, the air seals 52, 54 are influenced against the spindle 24 and their respective retaining rings 44, 46 and thereby provide excellent protection against air leakage. The air in the chamber 60 passes through the opening 78 into the cavity 34 and from there through the bore 80 to the outlet 64.

In accordance with one feature of this invention, a manual shut-off valve 22 is connected to the outlet 64. On the downstream side of the stop valve 22 is a manual fill line or valve stem 20. Accordingly, the user can manually fill the wheel 16 by closing the shut-off valve 22 to block. the outlet 64, so that the air can be supplied externally through the stem 20 which passes through the tube 18 back through the hub 30 which in turn is connected to a line 84 which enters the inner part of the wheel 16. Under normal working conditions, however, the air becomes the wheels automatically supplied.

Instead of modifying conventional wheel equipment when using the previously mentioned cuff construction, it may be desirable to arrange a completely new hub construction instead of or as a replacement for these hubs which are not designed for automatic inflation systems. according to

this thought is an alternative wheel-

equipment arranged as shown in fig. 6-9. To a large extent, the wheel equipment according to this alternative embodiment is quite similar to the equipment already described. Accordingly, the same reference numerals will be used to denote like parts. A main difference between the two versions is that the last version uses a new hub construction as opposed to the use of the conventional hubs mentioned in the first version.

With reference to fig. 6 - 8 shows a hub 30'

cast preferably in one piece of metal of malleable iron quality I or II. The central opening through the hub 30' is bounded by an annular inner surface generally designated by the reference numeral 83. A pair of projections 85, 87 are formed in the surface 83, one on each side of the cavity 34'. A pair of grooves 88, 89 are also formed in the surface 8 3 at a predetermined distance from the abutment 8 5 and 87 respectively. In this

with a minimal amount of customization. An annular cuff 42 has its outer edges connected, for example by welding, to the hub 30, so that the cuff 42 generally bridges the central cavity 34 in the hub 30. The inner parts of the cuff 42 include two separate grooves for receiving locking rings 44, 46. The cuff 42 also forms projections 48 and 50 which respectively counteract the locking rings 44 and 46.

The combination locking ring and shoulder in the cuff 42 defines a seat for receiving the outer peripheral surfaces of sealing rings 52, 54. The sealing rings 52, 54 are in the form of annular channels with open ends having a rigidly constructed outer main part and a flexible inner lip seal preferably made of synthetic rubber. Garter springs 56, 58 provide radially inwardly directed pressure forces on the flexible lip seals which abut against the outer surface of the spindle 24. This device defines an inner chamber 60 which surrounds the spindle 24. The sealing rings 52, 54 will be discussed in more detail later.

Provision is now made to provide a sealed air channel between an intake 62 in the non-rotating part of the wheel gear 14 and an outlet 64 in the rotating hub 30. A first bore 66 is drilled in the spindle 24, through substantially its entire length, preferably using of a rifle drilling technique. The left part of the bore 66 is sealed with a plug 68. Another downwardly directed bore 70 in the flange 26 is drilled until it abuts the right part of the bore 66. A substantially L-shaped connection 72 is welded to the spindle to extend the bore 70, as that it can be easily connected to an air source provided by a hose 74. A substantially right-angled directed opening 76 extends between the chamber 60 and the first bore 66 in the spindle 24. The sleeve 42 similarly includes an opening 78, so that the air can stand in connection between the chamber 60 and the cavity 34. A third bore 80 is then drilled in the hub 30 which extends into the cavity 3 4 to form a passage between the threaded outlet 64 and the cavity 34.

Air supplied to the intake 62 passes through the bores 70 and 66 and then out through the opening 76 in the stationary part of the wheel equipment 14. The air then exits through the opening i5569

gene 76 and into the chamber 60. Air is prevented from escaping to the external environment by means of the cuff 42 and the air seals 52, 54 which rotate with the hub 30. When there is compressed air in the chamber 60, the air seals 52, 54 are influenced against the spindle 24 and their respective retaining rings 44, 46 and thereby provide excellent protection against air leakage. The air in the chamber 60 passes through the opening 78 into the cavity 34 and from there through the bore 80 to the outlet 64.

In accordance with a feature of this invention, a manual shut-off valve 22 is connected to the outlet 64. On the downstream side of the stop valve 22 is a manual fill line or valve stem 20. Accordingly, the user can manually fill the wheel 16 by closing the shut-off valve 22 to block. the outlet 64, so that the air can be supplied externally through the stem 20 which passes through the pipe 18 back through the hub 30 which in turn is connected to a line 84 which enters the inner part of the wheel 16. Under normal working conditions, however, the air to the wheels automatically supplied.

Instead of modifying conventional wheel equipment when using the previously mentioned cuff construction, it may be desirable to arrange a completely new hub construction instead of or as a replacement for these hubs which are not designed for automatic inflation systems. according to

this thought is an alternative wheel-

equipment arranged as shown in fig. 6-9. To a large extent, the wheel equipment according to this alternative embodiment is quite similar to the equipment already described. Accordingly, the same reference numerals will be used to denote like parts. A main difference between the two versions is that the last version uses a new hub construction as opposed to the use of the conventional hubs mentioned in the first version.

With reference to fig. 6 - 8 shows a hub 30'

cast preferably in one piece of metal of malleable iron quality I or II.. The central opening through the hub 30' is defined by an annular inner surface generally designated by the reference numeral 83. A pair of projections 85, 87 are formed in the surface 83, one on each side of the cavity 34'. A pair of grooves 88, 8 9 are also formed in the surface 8 3 at a predetermined distance from the abutment 8 5 and 87 respectively. In this

embodiment, the hub 30' includes a number of evenly spaced inclined surfaces 90, 91 and 92 which are located within the annular surface for receiving the bearings. Such a construction makes it possible to easily remove the bearing equipment from the hub, e.g. to replace it. The storage devices can be removed with a device that has three backward curved fingers. The bearings are extracted by extending the fingers through the central opening in the bearing gear, expanding them into the inclined surfaces 90, 91 and 92 and then withdrawing them, taking the bearing gear with them.

With particular reference to fig. 8 and 9 are here

shown locking rings 44 and 46 arranged in slots 88 respectively. 89. The sealing ring 52 is held in place in the lateral direction between the locking ring 44 and the shoulder 85. In a similar way, the sealing ring 54 is held in place between the locking ring 46 and the shoulder 87 in the hub 30'.

Fig. 9 shows details of the sealing rings that can be used in both designs. The main part 9 3 of each sealing ring is made of a rigid material such as steel. The main part 9 3 delimits the vertical edge part and the outer peripheral part or leg of the device. The inner peripheral part is delimited by a mainly horizontally extending flexible lip 9 4 which is made of a polymeric rubber material with relatively high hardness. The lip 9 4 is preferably made of "nitrile polymer" with a hardness of 40 - 45 (durometer). In this particular embodiment, the lip 94 includes a tip 95 of wear-resistant material. In this example, the tip 95 is made of "Teflon" which is formed by including a ring of "Teflon" in the molding process when the lip 94 is made and then by machining the Teflon ring as desired. The tip 95 provides a self-lubricating contact surface which extends the sealing effect when there is little or no lubricant on the spindle 24. The outer surface of the main part 9 3 is preferably coated with a thin coating of sealing material. In the preferred embodiment, the coating 9 3 is a rubber-like polymer and more specifically made of nitrile polymer with a hardness of 10-15 (durometer). As an alternative to the use of a nitrile lip with a Teflon insert, the lip part can be made with "Viton" which shows good properties at high temperature and low friction.

It can now be understood that the sealing construction in both designs provides significant advantages compared to previously known constructions. It is relatively simple and easy to assemble because there are very few individual parts. The present invention further provides an excellent rotating seal which prevents air from escaping between the non-rotating and rotating parts of the wheel assembly. When the cavity 34 or 34' contains compressed air, the lips 94 of the sealing rings 52 and 54 are forced downwards against the non-rotating spindle

24 to form an excellent seal. The sealing rings are solid and are expected to show excellent wear resistance. It is also believed that the relatively large volume provided by the cavity 34 (34') in the hub can play a significant role in terms of

to speed up the inflation/deflation time of the automatic tire inflation system. The cavity effectively forms a small storage tank which is able to deliver a significant amount of air to the wheels. The cavity can also serve as a buffer zone to reduce the turbulence in the air flow to a minimum before it is led through the relatively small air channels in the remaining parts of the system. These advantages are particularly pronounced in the integrated hub construction in the latest version.

With reference to fig. 4 and 5 shall describe the automatic control system 100 for regulating the air pressure of the various wheel equipment. Fig. 4 shows the control system schematically, while fig. 5 schematically show the various components therein using well-known pneumatic symbols. Common elements on these two figures will be denoted by the same reference numbers where this is possible.

In the same way as for the Christmas equipment according to the present invention, the control system can be easily adapted for use in conventional military vehicles. In general, the control system uses a control box 101 which is mounted in the vehicle's 10 cab. Depending on the setting of a knee joint valve 102, the system for inflating or deflating the wheels works by supplying or extracting air through the manifold 104 which is connected to the respective wheels by means of hoses 74. In addition, the control system automatically maintains the wheels on

the pre-selected pressure and thereby adjusts increases or decreases in wheel pressure due to punctures, increased

working temperature etc.

The only source of air for the steering system is

from an air compressor 106 which is typically used for supplying compressed air to an air tank 108 used in the vehicle's air brake system. The air compressor 106 produces in a typical manner air pressure in the line 110 of about 8.44 kg/cm.

A very small amount of air from the compressor 16 is used as control air to control the switching of the inflation/deflation valves. The air can conveniently be drained from a connection 112 on a branch pipe under the dashboard, which supplies air to the vehicle's accessories, such as an air horn or window cleaners. The term "steering air" means that it is supplied from a source that is independent of the desired and actual pressure in the wheels. The air from the compressor 106 is fed through the intake line 114 to the control box in the vehicle's cab.

The intake line 114 is connected to an air filter 116 which removes dirt and separates water from the air. The output of the air filter 116 is connected to a check valve 118 to maintain a constant control pressure on the downstream side of the control system despite fluctuating air pressure supplied by the air compressor 106 which may be caused by the use of air brakes or wheel inflation. A set of three fixed pressure regulator devices are used to generate preset regulated pressures at their outlets. The pressure regulator device 120 is designed to provide 5.27 kg/cm of pressure at its output. The pressure regulator device 122 is designed for 2.11 kg/cm 2 while the pressure regulator 124 generates 0.7 kg/cm 2 at its output.

The outputs from the regulator device 120 and 122 are connected to the input openings of the selector device 102. The selector device 102 is a three-position knee joint valve which

in one position works to connect the output of the pressure regulator device 120 with the discharge line 126 while the line 128 is being emptied. In another position, the outlet from the pressure regulator 122 of 2.11 kg/cm 2 is connected to the outlet line 128, while the line 126 is emptied. In a third position, none of the outputs from the regulator devices 120 or 122 are connected to the lines 126 or 128, but instead the lines 126 and 128 are both emptied through the outlet opening 103.

The lines 126 and 128 are connected to opposite sides of a pendulum valve 130, the output of which is connected to one side of a pendulum valve 132. The opposite side of the pendulum valve 132 is connected to the output of the regulator device 124 for 0.7 kg/cm 2 over the line 134 The pendulum valves 130 and 132 work according to well-known principles, where the higher of the two pressures at their inputs is connected to their respective outputs. For purposes to be explained later, the pendulum valve 132 is biased at about 0.21 kg/cm so that the air passage from the generator 124 will be closed until the pressure on the other side of the valve 132 is 0.49 kg/cm 2 or less.

It will thus be understood that the pressure supplied to the output of the pendulum valves 132 will be either 5.27, 2.11 or 0.7 kg/cm 2 depending on the position of the selector device 102. This selected pressure will be referred to as the control pressure and it is connected via the lines 136 and 138 through the fire wall connection 140 to an inflation/deflation device 142. Pilot air is supplied in a similar way to the equipment 142 via the lines 144, 146 through the connections 148. If desired, a tire pressure gauge 150 can also be arranged in the vehicle's cab. The instrument 150 is connected to a static pressure tank 152 through lines 154, 156 through the bulkhead connection 158. The static pressure tank 152 has the relevant static pressure in the wheels. The tank 152 is connected to the wheels through a branch pipe 104 by means of the inlet line 160 which passes through air filters 162, 164 in a row on each side of a fixed opening 165 which limits the flow to and from the static pressure tank 152, so that the pressure in the tank 152 to any time is the same as that in the reels.

The equipment 142 for pumping up or emptying uses two rolling diaphragm pendulum valves 166 and 168 which work according to the main-secondary principle. The main valve 166 determines whether the wheels must be inflated, deflated or remain unchanged, as a function of the pressure differential between the desired steering pressure and the static pressure in the wheels. The secondary valve 168 works to deflate or pump up the wheels depending on the control determination made by the valve 166.

working temperature etc.

The only source of air for the steering system is

from an air compressor 106 which is typically used for supplying compressed air to an air tank 108 used in the vehicle's air brake system. The air compressor 106 produces in a typical manner air pressure in the line 110 of about 8.44 kg/cm.

A very small amount of air from the compressor 16 is used as control air to control the switching of the inflation/deflation valves. The air can conveniently be drained from a connection 112 on a branch pipe under the dashboard, which supplies air to the vehicle's accessories, such as an air horn or window cleaners. The term "steering air" means that it is supplied from a source that is independent of the desired and actual pressure in the wheels. The air from the compressor 106 is fed through the intake line 114 to the control box in the vehicle's cab.

The intake line 114 is connected to an air filter 116 which removes dirt and separates water from the air. The output of the air filter 116 is connected to a check valve 118 to maintain a constant control pressure on the downstream side of the control system despite fluctuating air pressure supplied by the air compressor 106 which may be caused by the use of air brakes or wheel inflation. A set of three fixed pressure regulator devices are used to generate preset regulated pressures at their outlets. The pressure regulator device 120 is designed to provide 5.27 kg/cm of pressure at its output. The pressure regulator device 122 is designed for 2.11 kg/cm 2 while the pressure regulator 124 generates 0.7 kg/cm 2 at its output.

The outputs from the regulator device 120 and 122 are connected to the input openings of the selector device 102. The selector device 102 is a three-position knee joint valve which

in one position works to connect the output of the pressure regulator device 120 with the discharge line 126 while the line 128 is being emptied. In another position, the outlet from the pressure regulator 122 of 2.11 kg/cm 2 is connected to the outlet line 128, while the line 126 is emptied. In a third position, none of the outputs from the regulator devices 120 or 122 are connected to the lines 126 or 128, but instead the lines 126 and 128 are both emptied through the outlet opening 103.

i5569 m

The lines 126 and 128 are connected to opposite sides of a pendulum valve 130, the output of which is connected to one side of a pendulum valve 132. The opposite side of the pendulum valve 132 is connected to the output of the regulator device 124 for 0.7 kg/cm 2 over the line 134 The pendulum valves 130 and 132 work according to well-known principles, where the higher of the two pressures at their inputs is connected to their respective outputs. For purposes to be explained later, the pendulum valve 132 is biased at about 0.21 kg/cm so that the air passage from the generator 124 will be closed until the pressure on the other side of the valve 132 is 0.49 kg/cm 2 or less.

It will thus be understood that the pressure supplied to the output of the pendulum valves 132 will be either 5.27, 2.11 or 0.7 kg/cm 2 depending on the position of the selector device 102. This selected pressure will be referred to as the control pressure and it is connected via the lines 136 and 138 through the fire wall connection 140 to an inflation/deflation device 142. Pilot air is supplied in a similar way to the equipment 142 via the lines 144, 146 through the connections 148. If desired, a tire pressure gauge 150 can also be arranged in the vehicle's cab. The instrument 150 is connected to a static pressure tank 152 through lines 154, 156 through the bulkhead connection 158. The static pressure tank 152 has the relevant static pressure in the wheels. The tank 152 is connected to the wheels through a branch pipe 104 by means of the inlet line 160 which passes through air filters 162, 164 in a row on each side of a fixed opening 165 which limits the flow to and from the static pressure tank 152, so that the pressure in the tank 152 to any time is the same as that in the reels.

The equipment 142 for pumping up or emptying uses two rolling diaphragm pendulum valves 166 and 168 which work according to the main-secondary principle. The main valve 166 determines whether the wheels must be inflated, deflated or remain unchanged, as a function of the pressure differential between the desired steering pressure and the static pressure in the wheels. The secondary valve 168 works to deflate or inflate the wheels depending on the control decision made by the valve 166.

The inputs and outputs of the valves 166 and 168 as well as their respective functions will be better understood with reference to the schematic representation in fig. 5. On

fig. 5, the positions of the pneumatic components are all shown with a depressurized system, i.e. in a neutral position. With particular reference to the valve 166, its control inputs 170 and 172 are connected to the selected control pressure over the line 138 and the static pressure in the wheels over the line 174 from the static pressure tank 152, respectively. The valve 166 includes two input openings 176, 178 and a drain opening 18 0 The control air through line 146 is connected directly to the inlet opening 176, but passes through a priority valve 182 before entering the inlet opening 178. The priority valve 182 is designed to close at a pressure less than approx. 5.27 kg/cm 2 for tasks to be explained later.

The control valve 166 also includes two output openings 184 and 186 which in turn are connected to the control inputs 188 resp. 190 on the valve 168. The arrows in the valves shown on

fig. 5 shows the mutual connections between the inlet openings and the outlet openings which are created in the three stages of the valve function. In the neutral stage, where pressure across the control inlets 170 and 172 is the same, the outlet openings 184 and 186 are connected back to the drain opening 18 0. When the pressure on the control inlet 170 is greater than that on the control inlet 172, control air from the inlet opening 176 will be connected to the outlet opening 186 and the outlet opening 184 are connected to the drain opening 18 0. In contrast, if the static pressure on the control inlet 172 is greater, then control air passing by means of the priority valve 182 through the inlet opening 178 will be connected to the outlet opening 184, but the outlet opening 18 6 emptied through the outlet opening 180.

The valve 168 works according to the same principle. It includes an inlet opening 192 and an outlet opening 194. The inlet opening 192 is connected to the output of the brake system air tank 108 through a priority valve 196. The priority valve 196 works to close when the pressure in the tank 108 falls below approx. 5.27 kg/cm 2 for reasons that will be explained later. The output opening 198 from the valve 168 is connected to a branch pipe 104, which, as already mentioned, is connected to the wheels through the wheel fittings 14. When the pressure above the control input 190 is greater than that of 188, the valve 168 works to connect the compressed air from the tank 180 through the input opening 192 to the exit opening 198 and thereby pump up the wheels. In contrast, when the control input 188 is supplied with higher pressure, the outlet opening 198 is connected to the drain opening 194, so that the wheels are deflated. When the pressures across the control inputs 190 and 188 are the same, no inflation or deflation of the wheels occurs.

When the vehicle's 10 engine is started, the compressor 106 fills the air tank 108 to a pressure of about 6.33 kg/cm o, after which the priority valve 196 opens and makes air available for inflating the wheels. Normally, the pressure in the tank 108 can increase to a maximum of 8.44 kg/cm 2 . If the pressure in the brake tank 108 falls below approx. 5.2 7 kg/cm , closes the priority valve 196 and thus allows the pressure in the brake tank to build up to a safe working pressure for the brake system, which takes priority over the system for inflating the wheels. The priority valve 196 also ensures priority air to the brake system in the event of a serious failure of the system for inflating the wheels.

To inflate or deflate the wheels, the user sets the knee joint valve 102 in one of the three pre-set positions. The valve 102 is preferably marked according to terrain or road conditions: One position (4.92 kg/cm 2 ) for road conditions, another position (2.11 kg/cm 2 ) for off-road driving and a third position (0.7 kg/ cm 2) for clay, sand or snow conditions.

It is assumed that the wheels are inflated to 0.7 kg/cm^ and the operator operates the knee joint valve 102 to the position corresponding to 5.27 kg/cm 2. The control system will automatically inflate the wheels and maintain them at this pressure without further manual intervention .

The output from the pressure regulator 120 (5.27 kg/cm 2 ) is connected at the selected setting of the knee joint valve 102 to the output line 126. The pendulum valve 130 allows only the higher pressure in the lines 128 and 126 to pass through, which in this case is 5.27 kg /cm 2 . The priority shuttle valve 132 similarly allows only the greater of the pressure in the line 134 or the pressure in the valve 130 to pass through. Consequently, the pressure of 5.27 kg/cm 2 becomes the new control pressure which is connected through the line 138 to the control input 170 on the valve 166. Since the right control input 172 is located at 0.7 kg/cm<2 > (the prevailing static pressure in the wheels) swings the valve 166 to connect control air from the line 146 through the inlet opening 176 and the drain opening 18 6 to the control inlet 190 of the valve 168. The right control inlet 188 of the valve 168 is connected to the drain opening 18 0 of the valve 166. Then the left control inlet 190 is above a greater pressure than the right control inlet 188, the valve 168 swings to connect the compressed air from the air tank 180 through the opening 192 with the drain 198 which in turn is connected to the manifold 104. The air is thus allowed to flow into the wheels and into the static pressure tank 152. The flow through the restriction in the fixed opening 165 is such that the pressure in the static tank 152

is the same as in any and all wheels to

2

At any time. When the wheels are pumped up to 5.27 kg/cm, the pressure in the tank 152 is also at this value. Thus, the right control input 172 on the valve 166 is now at the same pressure as the left control input 170. This brings the system into balance so that the valve 166 swings to the neutral position (as shown in Fig. 5) and blocks further control air from being supplied to the control inputs on the valve 168. Thus, this valve also swings to the neutral position and further closes the connection between the tank 108 and the branch pipe 104.

It is assumed that the vehicle is now on soft ground

and the user switches the selector device 102 to the third position (0.7 kg/cm 2 ). With the selector device 102 in this position (as shown in Fig. 5), the lines 128 and 126 are connected to the drain opening 103 of the pendulum valve 102. This makes it possible for the pressure of 5.27 kg/cm in the lines leading to the control input 170 of the valve 160, to be released backwards through the drain opening 103. The released pressure on the downstream side in the pendulum valve 132 must drop below approx. 0.49 kg/cm<2> before the valve 132 swings to allow the precisely controlled air pressure of 0.7 kg/cm 2 from the pressure regulator 124 instead of passing through the control valve 166. This gives an accurate control pressure at this value which does not other way would be

possible with a standard (non-biased) pendulum valve in this position due to the hysteresis effect.

With this pressure of 0.7 kg/cm applied to the control input 170 on the valve 166 and 5.27 kg/cm 2 still applied to the right control input 172, the system is no longer in balance. The control valve 166 is then swung to the left and connects control air from the inlet opening 178 to the drain opening 184 which is connected to the right control inlet 188 of the valve 168 w This causes the valve 168 to swing to the left in a similar way to connect the branch pipe 104 with the drain opening 194. In this way it is allowed air to flow from the wheels and the static pressure tank 152 out to the atmosphere until the pressures on both sides of the control valve 166 are the same, i.e. 0.7 kg/cm . At this point, valve 166 swings to its neutral position and shuts off the control air to valve 168, which in turn also swings to its neutral position and shuts off all air flow. The steering pressure, the pressure in the wheels, the pressure in the static tank and the wheel pressure gauge are now all equal to 0.7 kg/cm 2.

Care has also been taken to prevent unwanted emptying of the wheels in the event of a loss of air pressure that controls the valve device in the steering system. This loss of pressure can possibly occur when the vehicle is parked for a long time and causes the brake tanks to be drained and produces a loss of pressure. A break in the steering cable would also cause a loss of steering pressure. Under these conditions, the priority valve 182 prevents unwanted emptying of the wheels. The priority valve 182 is connected between the control air line 146 and the inlet opening 178 of the valve 166 which is used to empty air to

obtain pressure on the right pilot inlet of the valve 168. The priority valve 18 2 is designed to close at 5.2 7 kg/cm 2 . Correspondingly, if the pilot pressure were to drop below this latter value, no pilot air would pass through the valve 166 to the valve 168 and thus prevent valve 168 from opening

swing to the empty step.

It must also be recognized that the control system used in the present invention automatically maintains the previously selected desired air pressure in the wheels even if the conditions in the wheels may change. If e.g. there is a slight leakage 1 1 é>Y" nnntfprinfr i h-inleno iri 1 /-^on ctaf iel-o f r^ttf ant 1^9 sink below the preselected pressure and thereby cause the valve 166 and 168 to go over in inflated condition as necessary to maintain the desired pressure.' Similarly, if the temperature in the wheels increases so that the pressure in them is increased above the selected temperature, the valve device in the control system according to the present invention will automatically deflate the wheels until the desired pressure is reached. All this is achieved without any further manual intervention from the operator.

Those with experience in the field can now understand that the present invention offers various significant advantages compared to known systems for central wheel inflation. The described system is fully automatic and requires no intervention by an operator except to move the knee joint switch to the position that belongs to the terrain on which the vehicle moves. Once the selection is made, the system automatically adjusts and maintains the wheels at the selected pressure. The system also works very quickly.

It is able to empty all wheels (six pieces 14.00 times 20 wheels) to 0.7 kg/cm<2> from 5.27 kg/cm<2> within 3 min. and

40 seconds, much faster than known inflation systems. This is because the secondary valve 168 is quickly swung to its fully active positions once the main valve 166 has selected pumping or emptying. Both the wheel equipment and the air regulating control system are extremely economical by using a minimal number of components. In addition, the wheel inflation system described above can easily

fit conventional military vehicles with a minimal amount of modification. All these advantages appear at the same time as providing excellent reliability even under difficult conditions. The rotating air coupling in the present invention is isolated from harmful road conditions because it is placed inside and it is arranged without breaking into the load-bearing! structures or disturb the wheel bearings.

The various components of the just described automatic system for inflating the wheels can be incorporated as part of the conversion kit for the vehicle itself. The number of components in the kit will depend on the type of vehicle to be rebuilt and the extent of use of the various parts that the user wishes to retain. The set can e.g. include all new replacement parts for one or the other of the wheel equipment in the two designs along with all the new parts necessary to use the valve control system 100. It should be noted that the air compressor tank 108 will not normally be required because it is standard equipment on most vehicles that use air brakes. The vehicles may also already use wheel equipment capable of receiving an automatic system for inflating the wheels, but for economic reasons the vehicle does not include the valve control system. This would enable the manufacturer to mass produce a certain vehicle and then selectively choose which of these vehicles will include an automatic tire inflation system. Consequently, the vehicles that will be used on a certain surface can be modified in this way, while other vehicles used under less demanding conditions are not changed.

In these cases, the inlets and outlets that are in the pre-drilled wheel fittings will usually be plugged. The conversion kit would then include the parts that only make up the valve control system. The plugs can be removed in the wheel equipment and the valve control system easily added to thus equip the vehicles with an automatic system for inflating the wheels.

Professionals in the field will understand that the characteristic features according to the invention allow for easy installation in existing vehicles. The control box 101 can be easily mounted in the cab and the various pressure lines are laid up from the cab through the normal fireproof wall in the vehicle as shown in the drawings. The valve assembly 142 and manifold 104 are then mounted in a suitable location on the vehicle frame in the same manner as the static pressure tank 152. The various air lines can be easily interconnected at suitable locations to complete the conversion operation. As noted above, the contents of the kit may vary somewhat because the user may have flexible air hoses, connectors, tanks, etc. in stock. In these cases, the kit would only contain the control box 101 and the valve equipment 142.

Claims (7)

1. Conversion kit equipping vehicles with a system for automatic monitoring and control of wheel tire pressure, comprising a control box (101) mounted in a vehicle cabin and including manually operable selector means (102) for selecting one of several preset wheel pressure values tire (16) and valve means (142) which provide inflation/discharge of air under pressure and are mounted on the vehicle, characterized in that the valve means (142) comprise a number of valves (166, 168) with at least one valve (168) having first and other steering passages (190, 188), an outlet opening (198) arranged for connection to the wheels, an entrance opening (192) arranged for connection to a source (108) for compressed air and an outlet opening (194), the valve means (142) being operative to optionally connect the outlet opening (198) with the inlet opening (192) or the outlet opening (194) depending on the pressure difference between the desired and the actual wheel air pressure at a tank (152) for static pressure k with an inlet (160) connected to the wheels and a number of outlets (74) which give an indication of the current pressure in the tires (16), thereby automatically pumping up or letting air out of the tires to maintain the desired pressure selected by the user, and in that the vehicle's wheel assemblies (14) are equipped with sealing means (42, 44, 46, 52, 54) which, together with the wheel assembly's conventional geometry, provide a sealed air channel between an intake in non-rotating parts of the wheel and an outlet in rotating parts of the same. 2. Conversion kit according to claim 1, characterized by a filter/throttling device (162, 164, 165) with a fixed narrowing opening (165) connected between the inlet (160) of the tank (152) and the wheels. 3. Conversion kit according to claim 2, characterized by manifolds (104) with an inlet connected to the filter/throttling device (162, 164, 165) and the outlets (74) connected to the wheels. 4. Conversion kit according to claim 1, characterized in that the control box (101) includes a number of pressure regulating devices (120, 122, 124), of which each device produces a pre-set pressure at its output and can be selected by means of a selector device (102) where the output of the regulating device for the selected pressure and the output of the static pressure tank (152) is connected to a valve (166). 5. Conversion kit according to claim 1, characterized in that the sealing members (42, 44, 46, 52, 54) include a pair of sealing rings (52, 54), the outer peripheral surfaces of which are attached to a rotating part and the inner peripheral surfaces of the sealing rings rests against a non-rotating part of the wheel assembly (14). 6. Conversion kit according to claim 5, characterized by snap rings (44, 46) which attach the sealing rings (52, 54) to the non-rotating part of the wheel assembly (14). 7. Conversion kit according to claim 6, characterized by a sleeve (42) with an opening in its wall and receiving means (48, 50) formed in an inner peripheral surface of the sleeve for receiving the sealing rings.